Created Feature: Add ability to do some actions before and/or after installing the update [17]

Add ability to create "Custom Updates".

Custom Updates can perform some actions before and/or after installing the update.
These Actions can be :
* Create/Delete/Modify registry values.
* Create/Delete folders.
* Create/Delete/Modify files.
* Start/Stop/Unregister services.
* Run Executable file.
* Launch of VBS Scripts or Powershell Scripts.